I got a call from a client that has a water leak on a 3 story residential home. About 2.5 gal per hour leak. I looked at the water meter and saw the flow meter turning, so I shut the main inside the house and it stopped. So no leak on the main. Reopen valve.

Checked and shut all of the toilet supply valves, meter still turning. No faucet, hose bib or washing machine leaks leaks. Check pop off on HWH no leaks.
No humidifiers on the hot air system. No water softener.
Listened to the PVC stacks for water running, none. The house is part on slab and part unfinished basement. No leaks seen. It doesn't appear from a visual inspection that any of the supply lines go into the slab but rather up thru the wall. So I doubt it was leaking into the slab.

I shut the main at the meter and dropped the pressure and then reopened and the flow meter is rock solid, no more water flow from flow meter. What the?

i was scatching my head at this one too.....hey i was thinking, maybe its an underground leak. maybe from the citys piping and maybe its backing up into the house.....look forward to finding out what the prob is...please post it when you figure out what happened.post pics if you have any.kinda curious to see what kind of damage all of that water has done

I would have the water company change out the meter. They do go bad occasionally.

Last year, I also found I was leaking about the same amount of water from my vacation home, and could not find it anywhere. I finally had some experts come out and discovered I had a broken PVC tee fitting, right in the middle of my concrete patio slab.

In the first pic, you can see the change of color on the concrete slab, the severe cracking and the concrete falling due to the broken line. Second pic is the crack in the PVC fitting that caused all the damage. Third pic shows the slab jacked up with plumbing rerouted away from the slab, and the last pic shows the finished product, minus several thousand dollars!

I posted these pics so you can keep an open mind about what a broken line can do, and the damage it can cause.

My next move to identify the leak source is to pressurize the system with compressed air and then use my ultrasound leak detector to search the slab.

I don't think the water lines are in the slab but not 100% sure there not. Oh yea got a call from the client, the meter is spinning again. Here's another twist according to my client there have been a few other people in the neighborhood who have seen an increase in their water bill. With the same issues.

I don't think its a bad water meter cause I can hear the water running at the main valve just can't find a leak.

Just a thought but check to see if you have a pressure relief valve on the system....

It will probably look something like this...

Some areas use them and if the water supplier upped the pressure you'll probably have the whole neighborhood as a customer base....

They pour water down the drain without anyone knowing it's happening.

If it's what they have then install pressure reducing valves, potable water thermal expansion tanks and new T&P valves on the water heater while eliminating the relief valve and piping the gas direct to the combination gas valve.

There will be a strange valve where the T&P belongs on the water heater that shuts off the gas to the water heater. The valve will look like the one below....

Thanks Redwood, I'll have a look around for the relief valve. There already is a PRV on the main but the relief valve you mention makes sense. The neighborhood is 10-12 years old and I'll replaced a few PRV's already. Chance are if the relief valves are there the spring are worn out.I'll let you know what I find.

Do you have the ability to install a gate valve between the meter and the house, so when you shut the gate valve off, your meter stops completely? This was how I was able to isolate where my leak was coming from. I went the extra effort because I was certain it was a bad meter, only to find out that my leak was under the slab.